The invention relates to systems and methods for determination of cannabis impairment. In particular, the invention determines cannabis impairment by using a gyroscope assembly to sense the movement of a suspect and a computing device to analyze the movement during the performance of tests.
Driving under the influence of drugs has increased, while driving under the influence (DUI) of alcohol has decreased in recent decades according to Hartman et al., Drug Recognition Expert (DRE) Examination Characteristics of Cannabis Impairment (2016)(“Hartman”), which is hereby incorporated by reference herein.
With the legalization of marijuana in various states, cannabis has become a more common drug detected in drivers. Although cannabis use may be legal in certain states, it still can impair driving ability. Driving while cannabis impaired has been associated with approximately double the crash risk. See Hartman at page 220.
If an officer observes a person that may be impaired and who smells of marijuana, it is difficult to determine if that person is cannabis impaired to an extent that the law considers unsafe for certain activities such as driving a car.
Unlike blood alcohol content, THC content in blood is not a reliable measure of cannabis impairment. There is no detectable difference in cannabis impairment between a suspect with <5 μg/L and ≥5 μg/L blood THC. Hartman, at page 227.
Thus, determining if a person is cannabis impaired may involve several steps. First, an officer may observe signs (e.g., weaving or driving too slowly) and the driver has other symptoms (e.g., bloodshot eyes and smells of marijuana) that indicate a person is a suspect who should be checked for cannabis impairment. To establish if it is cannabis impairment, the officer may perform an evaluation that includes certain psychophysical tests (e.g., the modified Romberg balance test, the walk and turn, the one leg stand, and finger to nose).
In each psychophysical test, the officer states the instructions to the suspect and then asks the suspect to perform the test. Each test seeks to challenge the suspect's coordination, ability to divide attention and to follow directions. Many impairment clues depend on the officer's subjective evaluation and strict attention. The officer may be distracted by cars speeding nearby and suspect's behavior. Further, observations at night in poor lighting may hinder accurate observations of test performance. Further, the officer must accurately recall what he observed sometimes months later in court. To the inventors' understanding no one has used gyroscopes to quantify the movement while conducting psychophysical tests of a suspect for cannabis impairment.